(...) An example command line might look like this (for grub2, "kernel" is replaced by "linux"):

So, the one you are looking for is how to replace the kernel boot parameters. This is easily achievable modifying the GRUB_CMDLINE_LINUX_DEFAULT in the /etc/default/grub file. Then running su -c 'grub2-mkconfig -o /boot/grub2/grub.cfg' to update the script.

Next, edit /boot/grub/grub.conf or /boot/grub2/grub.cfg and add the "crashkernel=128M" command line option.

it means just add that to the end of the line in a menuentry { ... } block that begins with "linux" -- the first such block is usually the default, but whichever one you want, as long as you can remember at boot. Or all of them, if you want. They will all have (only) one such line.

Grub2 was supposed to eventually have some kind of CLI tool or console app you could use to configure stuff, which never materialized AFAIK. It's managed with some kind of sourcing and templating system, which most users can't be bothered with, so now they have yet another config file which says "do not edit" that everybody hack edits. Oh well. As long as it works...

With the upstream Grub2, and on Debian and derivatives, grub.cfg is generated by a script, and you must put custom additions in a file in /etc/grub.d. Does Fedora do things differently?
–
GillesFeb 26 '13 at 23:09